Forced circulation vapor generator



Aug. 22, 1939. T. MILLING 2,170,790

FORCED CIRCULATION VAPOR GENERATOR Filed' Feb. 14, 1959 INVEIN R ATTORN EYS Patented Aug. 22, 1939 vUNITED fsTATEs PATENT OFFICE i 2,170,190 roacnp cmcoLA'rIoN varon GENERA'ron Application February 14, 1939, seria No. 256,335

, m Germany ombel- 12, 193s 1a claims. (a. 12a-411) 'I'his invention relates to tubular vapor generators in which there is forced circulation of the working medium and in which the vapor generator heat exchange parts consistwholly or partly 5 of tube groups connected in series and also connected to distributors and collectors.

In steam generators of thistype it is a common practice to provide arrangements for distributing the circulated Water to the individual tubes oi groups of tubes arranged alongside each other. Diiiiculty is encountered with such distributing arrangements, however, when the tubes cannot be so arranged that the steam and water mixture only rises up in them but is also conducted through them either horizontally or downwards.

An object of the present invention is to provide an arrangement of the tubes and distributing means such that the direction of flow will correspond to the preponderance of either steam or B0 water in the mixture whereby those tube groups which carry a mixture in which the Water preponderates will consist for the most part of tubes in which the mixture is conducted generally horizontally or downwardly while those tube groups which carry a mixture in which the steam preponderates will consist for the most part of tubes in which the steam-water mixture is conducted generally upwards.

The invention is based upon the recognition of the fact that with an upward ow of a steam and water mixture the steam contained in the mixture favors the distribution since the steam has a tendency to flow up, Therefore, in those tube groups in which the steam content is already relatively great there exists a good distributing effect if the tubes of this group are so arranged that the mixture is conducted upward therein. On the other hand, in a tube group in which the water content of the mixture is in excess of the steam content, a good distribution may be obtained by arranging the tubes so that the ow of the mixture is either horizontal or in a downward direction, since water distributes itself on itself relatively well and, moreover, by reason of its heaviness in contrast to steam,` it has a tendency to flow downward.

Other objects and important features of the invention will appear from the following description and claims when considered in connection with the accompanying drawing, in which:

Figure 1 is a vertical sectional view through a forced circulation steam generator having one embodiment of the invention therein;

Figure 2 is a sectional and diagrammatic View of a forced circulation steam generator having a modied embodiment ofthe invention therein.

In the form of the invention illustrated in Figure 1, the water ows from the drum I to the circulating pump 2 and is forced by the pump 2 5 through the conduit 3 into the distributor 4.' Connected to the distributor 4 are a plurality of parallel tubes 5 constituting two sides of a water wall lining of the combustion chamber of the furnace, these tubes 5 being so arranged that they first conduct the water from above downwardly along one side of the combustion chamber and then horizontally across the bottom. The resulting steam-water mixture is collected in the intermediate collector 5. The intermediate collector 5 S serves at the same time as a distributor for the second group of parallel tubes 1. In this second group of tubes 1 the steam-water mixture is carried upwards.

'I'he provision of the intermediate collector 6 29 at the bottom of the combustion chamber carries with it the additional advantage that all the tubes of both groups,that is, groups 5 and l, can be emptied through this intermediate collector B.

The i'lring of the steam generator is indicated as being eiected through burners 8. Above the combustion chamber is shown another bank of steam generator tubes 8 through which water may be separately circulated. Moreover, above the generator S may lie, for example, a superheater 30 I0 and an economizer Il, not illustrated in detail.

In the illustrative example off the invention shown in Figure-2, the invention is incorporated in a steam generator having traveling grate ring but shown merely diagrammatically. From the drum I2 the water likewise flows downwardly to the circulating pump I3 and is forced by the pump I3 into the distributor or distributors I4, one

only being shown in the drawing. Connected to the distributor Il are a plurality of tubes I5 which form a side water Wall of the combustion chamber, the steam and water mixture produced in the tubes I5 being collected'in the collector I6. To provide the required lining of the combustion chamber, a like tube group can be arranged symmetrcally to-the tube group Il, I5, I6 upon the other side of the fire chamber or there can go out of the distributor I4 tubes I5 going both to the left side wall and to the right side wall.

From the collector I6 as well as from the col- 50 lector for the oppositely lyingv wall, if separate tube groups are provided, the steam and water mixture is conducted into the distributor I l to which parallel tubes I8 are connected, forming in the first instance, side walls for the other two 55 sides of the combustion chamber. 'rnetubes u discharge into the drum I2.

In the tubes II the water, together with the later forming steam, is conducted, in general, horizontally. To determine whether or not the Vsteam and water mixture in a given group is conducted upwardly or downwardly, the position ot the exit tubes under consideration in relation to the place at which the principal steam is produced is controlling. If this place lies higher than the exit, then we are generally dealing with downward ilow. In the case of tubes which are arranged for the greater part of their length horizontally, as for example the tubes l5, in Figure 2,

upward flow is, nevertheless, not to be spoken of, since this height diierence is only very small or, in other words, in respect to the last winding of the tube coil it practically exists not at all.

The invention is intended for steam generators which work with forced circulation, that is in which, from a collecting drum, a multiple of water in respect to the steam performance is circulated. With such steam generators consideration must be given to an especially good distribution, since they are operated mostly with constantly treated water so that with defective distribution the tubes tend to burn through or to be covered on the inside in a short time with salt.

What is claimedas new is:.. Y v

1. A forced circulation tubularsteam generator comprising, in combinationl groups oi tubes connected in series and in heat exchanging relation to a source of steam generating heat, each group being also provided with a distributor and collector and the collector of one. group serving as a distributor of a succeeding group, and means for insuring positive circulation of the water to be vaporized through said tubes, the initial group of said series conducting the steam and water mixture principally horizontally and having its collector located substantially at the lowest point o1' travel of the mixture and the succeeding group for which the said collector of the rst group serves as a distributor conducting the mixture therein principally upward.

2. A forced circulation tubular steam generator comprising a, plurality of tube groups `connected in series and each group being provided with a distributor and a collector, said tube groups being in heat exchanging relation'to a. source of steam generating heat and the collector of one group serving as a distributor for the succeeding group in the series, the collector for the last group of the series comprising 'a drum in which the steam and wtaer separates, a circulating pump having an intake from said drum and having a pressure conduit connected with the initial distributor of said series of tube groups, said groups being so arranged that the tubes in which the water preponderates in the steam and water mixture therein conduct the mixture principally horizontally and the tubes in which the steam preponderates in the steam and water mixture therein conduct the mixture principally upward, the combined collector and distributor which connects the said two groups of tubes being at the lowest point in said tubular generator.

TH. ZWILLING. 

